MEPS 524:83-94 (2015)  -  DOI: https://doi.org/10.3354/meps11127

Seagrass deterrence to mesograzer herbivory: evidence from mesocosm experiments and feeding preference trials

LaTina Steele1,2,3,*, John F. Valentine1,2

1Dauphin Island Sea Lab, 101 Bienville Blvd., Dauphin Island, AL 36528, USA
2Department of Marine Sciences, University of South Alabama, Mobile, AL 36688, USA
3Present address: Department of Biology, Sacred Heart University, 5151 Park Ave. Fairfield, CT 06825, USA
*Corresponding author:

ABSTRACT: Two laboratory experiments documented the effects of mesograzers (i.e. the gastropod Crepidula ustulatulina and the isopod Paracerceis caudata) on phenolic acid and condensed tannin production in 2 regionally abundant seagrasses—Thalassia testudinum (turtlegrass) and Halodule wrightii (shoalgrass). Subsequent paired choice experiments tested the hypothesis that phenolic acids and condensed tannins produced by these seagrasses deter mesograzer feeding. At the scale of the shoot, grazing by gastropods and isopods led to ~40 to 50% decreases in concentrations of some phenolic acids and ~20% decreases in condensed tannins in turtlegrass leaves. At a more refined spatial scale, concentrations of 2 of these compounds increased by 25 to 85% in areas near tissues damaged by C. ustulatulina and P. caudata in turtlegrass. In contrast, isopod feeding increased the concentrations of some shoalgrass phenolic acids by ~30 to 50%, while gastropod grazing led to ~25 to 50% higher concentrations of condensed tannins in shoalgrass leaves, suggesting that grazer identity and seagrass species play important roles in seagrass deterrent production. Amphipods (Batea catharinensis) consistently preferred agar food made from seagrass leaves with low phenolic concentrations in choice feeding experiments, indicating that phenolics can act as feeding deterrents to these mesograzers.


KEY WORDS: Thalassia testudinum · Halodule wrightii · Condensed tannins · Phenolics · Grazer


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Cite this article as: Steele L, Valentine JF (2015) Seagrass deterrence to mesograzer herbivory: evidence from mesocosm experiments and feeding preference trials. Mar Ecol Prog Ser 524:83-94. https://doi.org/10.3354/meps11127

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